Nuclear reactors are commonly used to produce electricity throughout various parts of the world. These nuclear reactors initiate and maintain a controlled nuclear chain reaction in a fissile fuel for the production of energy. The fissile fuel is commonly contained in bundles of tubes, referred to as a fuel assembly, for use in the nuclear reactor.
A pressurized water reactor ("PWR") typically utilizes a fuel assembly (hereinafter "PWR Assembly") which is approximately 81/2" square and 164" long. A boiling water reactor ("BWR") typically utilizes a fuel assembly (hereinafter "BWR Assembly") which is approximately 51/2" square by 176" long.
During the nuclear chain reaction, daughter particles originate in the fissile fuel as the fissile fuel disintegrates. Over time, the fissile fuel contains too many daughter particles to be efficiently used in the nuclear reactor. When this occurs, it is necessary to replace the fuel assembly containing the spent fuel.
Upon removal from the reactor, the spent fuel in the fuel assembly is very hot and very radioactive. Exposure to excessive radiation can present serious problems to humans and animals. Accordingly, it is necessary to store the spent fuel, without releasing excessive radiation, until the temperature and the level of radioactivity diminish to a sufficiently low level.
The spent fuel is stored at the nuclear plant in large cooling pools while waiting for the radioactivity of the spent fuel to decay to a safe level. As a result thereof, the cooling pools are beginning to become filled with the spent fuel at some plants.
Accordingly, there is a need to safely transport the spent fuel between plants with full cooling pools to those with available space. Further, plans are being developed for a nuclear waste site for storing the spent fuel. Thus, there will be a need in the future to safely transport the spent fuel to the waste site.
In many cases, the spent fuel must be transported with a truck and trailer since trains are not accessible to all nuclear plants. However, some states may attempt to block the transport of spent fuel on trailers on their highways. Nevertheless, under United States law, a particular state can not block passage of a truck and trailer which weighs under 80,000 pounds ("the legal truck shipping weight").
Presently, containers are available for shipping the spent fuel after the spent fuel has spent approximately ten years in the cooling pool. The Nuclear Regulatory Commission has provided strict guidelines for containers for transporting radioactive material. These containers must be able to withstand high and low temperatures, bumping, jarring and accidents which can occur during transport of the radioactive material, without allowing for the escape of predetermined levels of radioactive emissions or other contaminants.
However, many of the existing containers are too heavy for the legal truck shipping weight, are relatively expensive to manufacture, relatively expensive to maintain, and/or utilize complex piping.
Furthermore, some of these containers can only transport a relatively small amount of radioactive material in each shipment. The ability to transport more radioactive material per shipment is very significant since loading and shipping of the radioactive waste is very expensive due to the numerous precautions which must be taken during loading and shipping.
In light of the above, it is an object of the present invention to provide a container for radioactive material which can transport a substantial amount of radioactive material and still weigh less than the legal truck shipping weight. It is another object of the present invention to provide a container that can accommodate four PWR Assemblies or nine BWR Assemblies and be within the guidelines for radioactive emissions. Yet another object of the present invention is to provide a container which is not adversely affected by temperature fluctuations, minor accidents or jarring and is relatively inexpensive to manufacture and maintain. Another object of the present invention is to provide a container that is within the guidelines established by the Nuclear Regulatory Commission.